| In nearly two or three decade years, the conducting polymers have gradually developed into an area with great research value and concern. Among them, polypyrrole (PPy) has many advantages such as good thermal and chemical stability, high conductivity, easy synthesis, etc, is widely studied in the field of functional materials and devices. However, the application effect of PPy in these areas directly affected by its physical and chemical performance. Therefore, trying to improve or regulate its physical and chemical properties of PPy are gradually become a new hotspot in the current state of research. However, the morphology has close links with its physical and chemical properties in terms of PPy product with nanostructures. Because of PPy product with various morphology have disimillar in specific surface area, surface activity and quantum effect, which will lead to difference in its performance such as heat, light, electricity and magnetism properties. Thus, by adjusting the micro morphology of PPy products can effectively regulate its physical and chemical properties. In this paper, we used indigo carmine (IC) as the induced template of morphology to synthesis PPy product with novel and unique morphology of hexagonal spiral prismatic. And based on this template synthesis mechanism, more detailed researches were carried out about how IC concentration, FeCl3 concentration and pH in the synthesis system affect on the morphology, chemical structure and properties of PPy product.Firstly, PPy with morphology of hexagonal spiral prismatic was synthesized via chemical oxidation method, in which IC was used as the surfactant and dopant, FeCl3 was used as the oxidant. From the FT-IR analysis result, we found that IC molecule dope and grafte to PPy chain, and also found a vibration absorption peak of O-Fe-O. Further analysis by the resultes XPS and ICP-AES characterization, we found that Fe mainly distributed on the surface and very little in the mass ratio of whole quality of the PPy product. The synthesis mechanism of this kind of hexagonal spiral prismatic PPy nanorod was preliminary studied and summed up as:the polymerization of pyrrole monomer was limited in the hexagonal spiral prismatic micelles of IC-Fe (II) chelate which were changed from the previous formed cylindrical IC micelles during the chelated combing process of the carbonyl oxygen atom in IC molecule with Fe2+ reduced from Fe3+. The electromagnetism performance analysis found that the PPy product has the conductivity of 1.60 S/cm, and also has a certain wave absorption performance.Secondly, we further researched how IC concentration in the synthesis system affects IC micelle structure and the morphology and properties of PPy product based on the above template synthesis method of the spiral prismatic PPy. The effect mechanism was preliminary studied and concluded as:the structure of IC micelle change mainly attribute to the concentration increases of IC and the chelate degree between Fe2+ and IC molecule. Thus IC micelles in the structure of granular, rod and spiral prismatic were formed in the reaction system with the increase of IC concentration. Therefor, PPy product in the morphology of particle, nanorod and spiral prismatic were obtained when Py polymerize in the corresponding reacting template. The conductivity of PPy product decrease from 13.69 to 1.37 S/cm with the increase of IC concentration from 0.05 to 2.5 mM, however, the conductivity increases to 5.36 S/cm and then decline to 3.96 S/cm when the concentration of IC further increase to 10 mM. The conductivity decrease mainly attribute to the over doping and adsorbing of IC molecule which would hinder the charge transfer, and the conductivity increase related to the spiral gap increases of spiral prismatic PPy. Moreover, we found that the spiral prismatic PPy with layer structure has the best absorbing properties among the morphology of particle, nanorod and spiral prismatic on micro-scale, because its structure is helpful to have a multiple scattering effect to absorb electromagnetic waves.And basis on this, we further studied how FeCl3 concentration in the synthesis system affects the morphology and properties of PPy product. The SEM result show that the morphology of PPy product change form particle to spiral prismatic and then to columnar when the FeCl3 concentration increase from 0.01 to 0.30 M. The synthesis mechanism was preliminary studied and concluded as:the oxidation potential in the synthesis system with the FeCl3 concentration of 0.01 M is too low to prompt PPy from low polymer to high polymer, and PPy in the morphology of particle is obtained. However, the oxidation potential in the synthesis system increase with the rising of FeCl3 concentration, which would benefit for PPy from low polymer to high polymer, and obtained PPy product in the morphology of spiral prismatic. Moreover, the Fe2+ concentration increase with the FeCl3 concentration further increase, which would lead to its chelation with cylindrical IC micelle more sufficiently, making the spiral gap of the spiral prismatic IC-Fe (II) chelate micelle decreases and the morphology of prepared PPy also changed from spiral prismatic to columnar. The conductivity of PPy product decrease from 7.60 to 2.53 S/cm with the increase of FeCl3 from 0.03 to 0.07 M, however, the conductivity increases from 2.53 to 13.93 S/cm when the concentration of FeCl3 further increase from 0.07 to 0.30 M. The reflection loss result show that PPy with the morphology of particle and spiral prismatic have better absorbing property, and the former has the maximum absorption peak reached 19 dB in the thickness of 2 mm.Lastly, we further investigated how pH value in the synthesis system affects the morphology and properties of PPy product. The affect mechanism was preliminary studied and concluded as:when HC1 is added to the reaction mixture, it weakens the hydrogen bonding between adjacent IC molecules and inhibits the chelation between Fe+ and IC, thus further inhibiting the morphology transform of IC micelles from cylinders to hexagonal prisms. Moreover, the inhibition is gradually strengthened with the decrease of the pH. Therefore, the structure of IC-Fe(II) micelles change from hexagonal spiral prisms to spirals and then to rugby-like and spherical shapes and the morphology of PPy change from spiral rods to nonspiral rods and then to particles. Further study demonstrates that the conductivity of PPy decreases from 1.91 to 0.62 S/cm with its morphology changed from spiral rods to nonspiral rods and then to particles when pH value decrease from 2.6 to 1.5, as a result of gradually increased contact resistance and the degree of electron delocalization. With the decrease of the pH value from 2.6 to 1.5, the maximum reflection loss of PPy gradually increases from 5.99 to 9.65 dB and the corresponding loss peak moves to higher frequency points simultaneously. |
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